The present invention relates to devices for controlling a distribution of power to subsystems, for example to a main device and at least one secondary device or a plurality of secondary devices.
More particularly, the present invention relates to the above mentioned devices formed as electrical power strips and power control sensors which can be used with new devices having two modes of operation, standby or off and full on, with the use of main device or secondary devices.
One type of an electrical distribution device is the power strip or power control center, which generally comprises of a row of power outlets, switched or unswitched, to distribute power to a primary device and secondary device(s) from a standard outlet (e.g., wall outlet). Some power strips and control centers contain options like circuit breakers, fuses and/or surge protectors, for example.
In newer personal computers the system can turn itself off and is controlled by the operating system. During the system shutdown, there is a delay in which the operator must wait for the system to finish before turning off the secondary device(s). Depending on the operating software and programs, this can be a long time. Using this invention, the user may leave after the shutdown is started. When the system finishes and switches off or to the standby mode, the secondary device(s) will be turned off.
When used with computer devices, each device is plugged into a separate outlet with the computer plugged into the main outlet. When the computer is turned on, the current level increases to a high enough level to turn on the secondary device(s). Other constant power outlets may also be included for wake up devices, such as modems capable of bringing the system out of standby mode.
U.S. Pat. No. 4,731,549; U.S. Pat. No. 4,825,140 and U.S. Pat. No. 4,970,623 are methods for controlling secondary device(s). All require internal power supplies and many components, making them too expensive for mass production and difficult to fit in a standard power strip.
Some improved solutions are disclosed in our patent applications Ser. Nos. 09/521,029; 09/553,355; 09/953,743.
Accordingly, it is an object of present invention to provide a device for controlling distribution of power to subsystems, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a device for controlling a power distribution to subsystems which has a power input to connected to a power source, a primary power output to be connected to a primary device, at least one secondary power output to be connected to at least one secondary device; sensing means for sensing when a current level falls below a threshold in response to the primary device being turned off and when the level current raises above a threshold in response to the primary device being turned on; and executing means operatively connected with said sensing means and operative for interrupting a power supply to said at least one secondary device when the sensing means sense the current level below the threshold and supplying power to said at least one secondary device when said sensing means sense the current level above the threshold. A power limiting means for limiting voltage across said sensing means and a low current operating means which increases the voltage to provide triggering of said executing means despite the limiting of the voltage by said power limiting means.
By using power limiting means with a low voltage drop, the heat produced at high current draws though the main power output will be small, allowing the device to be placed in smaller housing.
In accordance with the invention a power limiting means include two diodes which are arranged in opposite directions across said sensing means.
Also in accordance with the invention a low current operating voltage increasing means include a voltage divider means.
In accordance with a further embodiment of the present invention, the sensing means can be formed as a current sensing resistor arranged in series with a power input of the device.
The executing means can be formed for example as a DC relay, as an AC relay, as a solid state AC relay, etc.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.